The present invention relates to a disk drive, a fabrication method thereof, and a disk-drive controller.
Concentric, circular recording tracks X2 are formed on the recording surface of a magnetic disk X1 that is employed as a storage medium in a disk drive, as illustrated in FIG. 2. The recording surface is also provided at each predetermined angle (e.g., 360xc2x0/80, or 45xc2x0) with a servo area X3 on which a servo sector that, includes a servo pattern and an ID number, etc., is recorded. Between adjacent servo areas X3, the recording surface is further provided with a data area X4 on which a data sector X5 is recorded. Also, in some disk drives, this data area X4 is segmented into several zones in the radial direction of the magnetic disk X1. For each data zone, the number of data sectors X5 is optimized in accordance with the radial position of the zone in order to make the recording densities on the data zones uniform.
In addition, a servo pattern (which consists of WEDGE-A, WEDGE-B, WEDGE-C, and WEDGE-D) and an ID number (CYLID) are recorded on the servo area X3, as shown in FIG. 3. If a read/write head X6 passes over the servo pattern and ID number, the outputs of the servo pattern and ID number reproduced by the read/write head X6 are supplied to a HDC/MPU X9. If these reproduced outputs are supplied, the HDC/MPU X9 calculates the current position of the read/write head X6, based on these outputs.
In a disk drive such as this, if the data sector X5 is specified and recording/reproduction is instructed, seek control is performed so that the read/write head X6 is moved to a target track on which the specified data sector has been recorded. After the read/write head X6 has reached the target track, a track-following control of adjusting the position of the read/write head X6 is performed so that the read/write head X6 follows the target track. In this manner, recording/reproduction is performed on the specified data sector.
The HDC/MPU X9 calculates an error (i.e., position error) between the target track and the current position of the read/write head X6 based on the reproduced output of the above-mentioned servo pattern. Furthermore, the HDC/MPU X9 executes control in accordance with the position error.
If the target track is specified, the HDC/MPU X9 first executes a control of accelerating the read/write head X6 toward the target data sector. Then, if the moving speed of the read/write head X6 has reached a predetermined maximum speed, the HDC/MPU X9 executes a control for moving the read/write head X6 at a constant speed. Finally, if the read/write head X6 has arrived near the target data sector, the HDC/MPU X9 executes a control of decelerating the read/write head X6 (settling control).
If the read/write head X6 reaches the target track, the HDC/MPU X9 switches the settling control to the track-following control of causing the read/write head X6 to follow the target track. The switching of these controls is performed by changing an arithmetic parameters that calculate servo data.
The seek control and the track-following control are executed by calculating servo data that is used for driving a voice coil motor (VCM) X8 that moves a head arm X7. The servo data is calculated based on the position error by the HDC/MPU X9.
Specifically, the calculation of this servo data is executed according to the following Equation (1), which includes an integral parameter I from the standpoint of the stability of control.
U(t)=K1xc3x97X(t)+K2xc3x97[X(t)xe2x88x92X(txe2x88x921)]+K3xc3x97U(txe2x88x921)+K4xc3x97U(txe2x88x922)+K5xc3x97I+Cxe2x80x83xe2x80x83(1)
Since it is becoming necessary to perform servo control at high speeds and with a high degree of accuracy (dynamic range) in recent years, accuracy in the above-mentioned calculation of the integral parameter is also increasingly being demanded. As a result, there are cases where the integral parameter will exceed the accuracy of arithmetic means"" control equipped in the HDC/MPU X9.
If the calculation accuracy of the integral parameter exceeds the accuracy of the arithmetic means"" control, an accurate calculation of servo data cannot any longer be made. As a result, the track-following control to a target track cannot any longer be performed and recording/reproduction of data becomes impossible.
Also, if the calculation accuracy of the integral parameter exceeds the accuracy of the arithmetic means during manufacturing test process, the disk drive will then be considered to be defective and reduce yield.
In addition, in order to realize the calculation accuracy required, it is also possible that the enhancement of calculation accuracy of an arithmetic unit equipped in the HDC/MPU X9 adding or separate arithmetic means such as DSP. Accuracy of an arithmetic unit equipped in the HDC/MPU X9 or DSP, however, is discrete like next unit of 16 bits is 32 bits, resulting in too much increase in cost.
The present invention has been made in view of the above-mentioned problems. Accordingly, it is an object of the present invention to provide a disk drive, a manufacturing test method thereof, and a disk-drive controller which are capable of improving yield without increasing costs (to more than necessity).
To solve the above-mentioned problems, the disk drive according to the present invention is characterized comprising:
a disk storage medium with a servo area on which a servo sector is recorded and a data area on which a data sector is recorded;
recording/reproducing means for performing reproduction of said servo sector of said disk storage medium and recording or reproduction of said data sector;
drive means for driving a position of said recording/reproducing means;
position detection means for extracting position information indicating the position of said recording/reproducing means from output of said servo sector reproduced by said recording/reproducing means;
holding means for holding an integral parameter in accordance with a position on said disk storage medium;
arithmetic means for calculating data for driving said drive means, based on said position information detected by said position detection means and said integral parameter in accordance with said position information; and
correction means for setting said integral parameter in accordance with calculation accuracy of said arithmetic means and correcting the calculation made by said arithmetic means.
Also, the disk drive may be provided with:
seeking-error detection means for detecting that a seek operation of moving said recording/reproducing means to a target position in accordance with a result of the calculation made by said arithmetic means has failed; and
reset means for setting said integral parameter again when failure of said seek operation is detected by said seeking-error detection means.
In addition, a disk-drive manufacturing test method according to the present invention is characterized comprising the steps of:
moving said recording/reproducing means to all radial positions on said disk storage medium which are employed in recording and then calculating an integral parameter at each radial position; and
adjusting said integral parameter to a value within the calculation accuracy of said arithmetic means when said integral parameter exceeds the calculation dynamic range of said arithmetic means.